Zaherite
Chemical formula: Al<sub>12</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>5</sub>(OH)<sub>26</sub>·20H<sub>2</sub>O
Zaherite is a very rare hydrated aluminum sulfate, forming microscopic, fibrous aggregates of white or bluish color.
Properties
- Mohs hardness
- 3
- Luster
- Earthy
- Streak
- White
- Density
- 1.88
- Cleavage
- Perfect on {010}, Good on {100}
- Fracture
- Uneven
- Transparency
- Opaque
- Crystal system
- Triclinic
Diagnostic features
## Identification Macroscopic identification of zaherite is practically impossible without advanced analysis. Indicative features may include: extreme rarity, occurrence as white, dull, chalk-like masses in a specific geological environment (e.g., in association with alunogen). Its low hardness and reaction to water are characteristic. Definitive identification requires X-ray diffraction (XRD) or chemical (EDS) analysis. ## Distinguishing from Similar Minerals Zaherite can be confused with other white, earthy sulfates, such as alunogen, gypsum, or epsomite. It is distinguished from them by its chemical composition (it is an aluminum sulfate, not calcium or magnesium) and its unique X-ray diffraction pattern. Unlike gypsum, it is much softer and has a different aggregate structure. ## Crystal Forms Zaherite forms microscopic crystals in the form of elongated lamellae or fibers, which combine into massive, earthy, chalky, or porcelain-like aggregates. Individual, well-formed crystals are not observed.
Geological environment
## Genesis Zaherite is a secondary mineral. It forms as a result of weathering processes of rocks rich in aluminum and sulfides, under low temperature and pressure conditions. Its formation is associated with the activity of sulfate-rich solutions. In its type locality (Pakistan), it was found in a laterite block enclosed within a rock salt deposit. ## Mineral Associations This mineral co-occurs with other sulfates and secondary minerals. It is most commonly associated with: alunogen, halite, sylvite, gypsum, and also iron oxides. ## Localities Zaherite is an extremely rare mineral, known from only a few localities worldwide. Besides the type locality in the Salt Range, Pakistan, its occurrence has also been reported in Yemen and in the La Compania mine in the Spanish province of Almería.
Rarity
Extremely rare
For collectors
## Quality Criteria Due to its extreme rarity, every analytically confirmed zaherite specimen has high scientific and collector value. The most desirable specimens are those where the mass of zaherite is as large and as pure as possible, with a visible fibrous or chalky structure. A well-documented locality and the presence of associated minerals confirming the paragenesis are also important. ## Popular Localities The only source of specimens available on the collector's market is its type locality in the Salt Range, Pakistan. Specimens from other, few localities practically do not appear in circulation.
Care and storage
## Cleaning Zaherite specimens are extremely delicate and sensitive to water. They should not be wet cleaned. Only very careful removal of dust with a soft brush or a stream of compressed air from a distance is permissible. ## What to Avoid Contact with water must be absolutely avoided, as it can dissolve or damage the mineral. All chemicals, ultrasonics, and high temperatures should also be avoided. The mineral is very soft and susceptible to mechanical damage. ## Storage Zaherite specimens should be stored in a dry place, preferably in a sealed container (e.g., a "membrane box") or a box with a desiccant. They should be protected from dust, vibrations, and direct contact with other minerals.